1. Field of the Invention
The present invention relates to a trouble diagnosis apparatus for a device controlled by a programmable controller.
2. Prior Art and Prior Application
Conventionally, when a device or devices controlled by a programmable controller develop trouble, the troubleshooter finds a fault location by observing the fault conditions or inspecting them through a synchroscope or multimeter.
However, this method takes much troubleshooting time and further requires a troubleshooter who has full knowledge of the sequence circuits and the device in order to securely find fault locations.
To overcome the above-mentioned problems, a model pattern of change in input/output signals obtained when the device is operating normally is previously formed manually, in order to check whether the actual pattern matches the model pattern when the device is operating by a diagnostic program incorporated in the programmable controller. In this method, however, there still exists a problem in that it takes much time to prepare the model pattern of input/output signal changes. Further, this model pattern can be prepared by only a person who has full knowledge of the sequence circuits. In addition, there exists a probability that trouble occurs at locations not represented by the model pattern.
As described above, where trouble diagnosis by the programmable controller is dependent upon such a method that input/output conditions anticipated when trouble occurs are previously examined by the user itself so as to be incorporated in the user program, complicated work is required for setting trouble conditions and programming. Therefore, once the user program has been completed, it is extremely troublesome to incorporate a trouble diagnosis program in the user program.
To overcome the above problem, a novel trouble diagnosis apparatus has been proposed in Japanese Patent Appln. No. 60-190658 (Laid Open No. 62-49518), in which a programmable controller is operated actually to learn the transition of input/output pattern conditions, and the normal operation is monitored by comparison between the previously learned pattern conditions and the actually operating pattern conditions.
In the diagnosis apparatus as described above, although the user itself need not set trouble conditions, there still exists a problem in that when a plurality of asynchronous controlled devices must be controlled simultaneously, it is difficult to accurately determine trouble conditions.